1. Field of the Invention
This invention relates to improved processes for the production of monohydroxy monocyclic acetals and their esters, e.g. trimethylolpropane cyclic formal (TMPF), and its acrylate ester (THPFAcA).
2. Background of the Invention
Monohydroxy monocyclic acetals and certain of their esters are known in the art. Thus, U.S. Patents Nos. 4,076,727 issued Feb. 28, 1978 to Zey et al., and 4,207,155 issued June 10, 1980 to Martin et al., disclose the production of monohydroxy monocyclic acetals by reacting a trihydroxy alcohol selected from the group consisting of trimethylolpropane (TMP), trimethylolethane (TME), and compounds having the formula: ##STR1## where n is 1 to 4, e.g., glycerin, with an aldehyde selected from the group consisting of formaldehyde or a formaldehyde source, C.sub.2 -C.sub.4 aldehydes, e.g. butyraldehyde, and C.sub.2 -C.sub.4 halogenated aldehydes, e.g., chloral. As an illustration of this reaction, Example 1 of each of the cited patents shows the reaction of trimethylolpropane with formaldehyde in the presence of benzene using para-toluenesulfonic acid as catalyst to produce a crude product. The latter is then refluxed to remove water, cooled, extracted to remove catalyst, dried, solvent stripped to remove benzene, and distilled under vacuum to obtain an 87% by weight yield of what is assumed to be the monohydroxy monocyclic trimethylolpropane formal. (TMPF).
After formation of the monohydroxy monocyclic acetal, e.g., TMPF, it may be formed into an ester, e.g., an acrylate or methacrylate ester using one of the three methods disclosed in Patent No. 4,207,155, viz., transesterification with a low boiling ester containing the desired acid moiety, e.g., ethyl acrylate, using a transesterification catalyst, e.g., a titanium ester; reaction with acryloyl chloride or methacryloyl chloride; or direct esterification with acrylic or methacrylic acid using an acidic acetal formation catalyst. The monocyclic acetal acrylates and methacrylates are stated in Patent No. 4,076,727 to be "useful in practically any end use where vinyl polymerizable monomers are utilized. In addition, they are particularly useful as diluents in unsaturation-containing coatings, particularly as diluents in ultraviolet curable coating compositions."
Also of interest is British patent No. 1,166,366 which discloses various means for the formation of cyclic acetal esters including reaction of a cyclic acetal alcohol with a halide or anhydride of the esterifying acid in the presence of an equivalent amount of a base such as pyridine, or reaction of the cyclic acetal with the esterifying acid or its anhydride in the presence of a separate, strongly acidic catalyst; and European Patent Application Publication No. 165,164 which teaches on pages 6 and 7 the acylation of mixed glycerol formals with acetic anhydride in the presence of pyridine.